It is known that in the course of advanced technological operations and more particularly with the production of electric energy by means of atomic or fossil fuelled power stations large amounts of heat are set free which have to be dissipated to the environment.
As a rule, such heat amounts are carried off by still or river waters though such possibilities seem to approach exhaustion and, therefore, recooling of water by means of suitable apparatus is preferred recently which transmit the heat to be dissipated to the ambiency.
Two kinds of such water recooling apparatus are known under the terms wet coolers and surface coolers, respectively. A third group is formed by what are called direct coolers which operate without the intermediary of water and in which the work medium of a plant is directly cooled down by means of air.
With wet coolers the cooling water warmed up in a power plant or in a technological process is caused to contact atmospheric air so that it partly evaporates and, thereby, cools down. The picked-up heat is transmitted by convection and particularly by evaporation to the ambiency. The cooled-down water can again be used for cooling purposes.
In case of surface coolers the warmed-up cooling water is not directly contacted with air. Instead, it flows through a cooler or heat exchanger the surface of which serves for transmitting heat to the ambient air. The cooling water is cooled down thereby and may again be made use of.
With direct cooling the work medium to be cooled down such as in most cases the steam of power plants will be supplied likewise into a cooler or heat exchanger the surfaces of which are exposed to atmospheric air.
Each of the above described cooling methods requires the circulation of considerable amounts of air which is obtained either by means of blowers driven by electric motors, or by employing towers or chimneys which make use of the natural upward drift of warm air.
With large new industrial establishments and more particularly with atomic and thermal power plants cooling towers of natural lift become increasingly important since they are solely capable to economically circulate the excessively large amounts of air required by the operation of such plants. As is known, wet cooling towers as high as 100 to 150 meters and of diameters of 100 to 120 meters have been built recently. Dry cooling towers in accordance with the system Heller, where condensation by air ("air condensation") is obtained in surface coolers or heat exchangers, have been built in similar sizes.
It is frequently required that such industrial plants or their cooling apparatus be arranged underground for reasons such as landscape conservation or prevention of potential damages due to war.